Different types of feed water (e.g., brackish water, seawater, treated wastewater, etc.) can be treated in order to be purified and converted to fresh water so it is suitable for human consumption, irrigation or industrial use. This water can be treated by different techniques, one of which is the reverse osmosis technique. According to this technique, pressure is used to force salty feed water against membranes sheets disposed in a membrane element which allow relatively salt free water to pass through. The membrane sheets which are used for reverse osmosis can have a dense barrier layer in a polymer matrix where most separation occurs. The water can are be treated in other techniques such as nanofiltration and ultrafiltration, in which other types of membranes can be used. In most cases, the membrane sheet is designed to allow only water to pass through this dense layer, while preventing the passage of solutes (such as salt ions). This process requires that a high pressure be exerted on the high concentration side of the membrane element, usually 40-70 bar for feed water which is seawater, which has around 27 bar (390 psi) natural osmotic pressure that must be overcome.
The membrane element in which the membrane sheets are disposed is usually installed inside a pressure vessel. From time to time, there may be a need to extract the membrane element from the pressure vessel for different necessities such as maintenance or replacement. The extraction of the membrane element from the pressure vessel can be a difficult task, for example, when the membrane element is tightly received within the pressure vessel, when the pressure vessel is disposed high in the desalination system, or when there is an accumulation of salts between the membrane element and the pressure vessel.
Therefore, there is need to develop a method according to which the membrane element can be manipulated and moved within the pressure vessel.